Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be accessed by various types of mobile devices (e.g., access terminals) adapted to facilitate wireless communications, where multiple access terminals share the available system resources (e.g., time, frequency, and power). Examples of such wireless communications systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems and orthogonal frequency-division multiple access (OFDMA) systems.
In several different wireless communication technologies, a power-saving technique called discontinuous reception (DRX) or a slotted mode may be used. In DRX, a mobile device (e.g., an access terminal, sometimes called a mobile station or user equipment) goes to sleep by turning off certain relatively power-intensive circuitry, and periodically wakes up to look for information transmitted at the appropriate times. In slotted mode, the mobile device monitors those time slots that are assigned to it. In CDMA, for example, the mobile device wakes up according to a slot cycle index (SCI) for decoding mobile terminated directed messages during the assigned slot or for performing registrations.
A larger SCI value increases the time duration between wake-up periods. During slotted mode operation, the mobile device may wake up and determine reacquisition slew (drift in pilot timing) by searching the strongest pilot path using an active set window with a suitable size (e.g., ASET_WIN_SIZ). In certain category of mobile-to-mobile (M2M) devices, a M2M device may operate with higher SCI values. Therefore, the M2M device may be configured to have longer registration time duration in order to restrict the frequency of network access. However, if the SCI value is too large, the M2M device may fail to reacquire the system when the reacquisition slew becomes too large due to long wake-up cycle.